The present invention relates generally to the field of tube extraction, and more particularly to an improved apparatus and method of removing tubes and/or tube stubs from structures comprising multiple tubes, such as boilers, condensers, evaporators, drums, and the like.
A typical heat exchanger comprises a pair of parallel tube sheets, a plurality of baffle plates, and a plurality of heat exchanger tubes. The tube sheets are located at the ends of the heat exchanger. The baffle plates are positioned between the tube sheets and generally parallel thereto. The tubes extend between the tube sheets and through the baffle plates and are supported by the tube sheets. The tube sheets and baffle plates have a series of aligned holes formed therein, and the tubes are inserted through these holes and then expanded in the areas of the tube sheets into fluid-tight pressure contact therewith.
In the course of normal preventative maintenance and/or repair it may be necessary to remove and replace one or more tubes from the structure. This process generally begins by cutting the tubes to form a tube stubs protruding several inches from the tube sheet. The expanded fluid tight pressure contact ends of the tube stubs are then withdrawn from the sheet by forced or deformation.
Various tools are known for removing tube stub, such as wedges that mechanically deform the tube stub, collapsing the tube inward upon itself. Anvils and hammers are also readily used to mechanically force collapsed and uncollapsed tubes out a tube sheet hole or bores.
Additional prior art tube stub removal devices include:
U.S. Pat. No. 4,355,450 to Miller discloses a tube extracting mechanism having a wedge with expandable circumferential gripping teeth.
U.S. Pat. No. 3,791,011 to Keys shows a tube pulling device with longitudinally fixed radially expanding gripping means which engages the tube wall for withdrawal of the tube from the tube sheet.
U.S. Pat. No. 3,507,028 to Stellatella shows a hydraulic tube puller with radial expansion of an inner end portion of a tube gripping member into the tube wall.
The primary problem with all these prior art structures is the imposition of expansion force on the tube precisely at the point where it is engaged with the tube sheet which can damage the metal between adjacent holes and cause the holes in the tube sheet to enlarge and not properly grip a new tube when it is expanded. Moreover, the prior art devices require multiple devices, increasing the likelihood of breakage of the removal devices, and resulting in an increase of down-time of the structure for repairs.
U.S. Ser. No. 11/762,104, herein incorporated by reference, discloses a recent innovation that overcomes many problems encountered during traditional tube stub removal. U.S. Ser. No. 11/762,104 teaches a method of tube stub removal wherein a metal tube stub is heated then subsequently elongated and circumferentially contracted for the purpose of readily removing a tube from a tube sheet. While a beneficial method over prior art, the method of Ser. No. 11/762,104 requires multiple operators thereby increasing tube removal costs and down time related to tube removal. Accordingly, a need exists for an improved method of tube stub removal that require only a single operator and overcome deficiencies of the prior art.
The present invention improves upon the method of tube stub removal disclosed in U.S. Ser. No. 11/762,104, and provides a novel apparatus that allows a single operator to readily remove a tube stub from a tube sheet without damaging the tube sheet, in addition to the additional advantages as discussed herein.